Stand for a surgical microscope

ABSTRACT

A stand for a surgical microscope is suggested, comprising a vertical support, at least one horizontal support, a first vertical articulation unit that is connected the horizontal support, a second articulation unit determining an oblique pivot axis, a displacement unit that is attached to the second articulation unit and has multiple degrees of freedom for displacement and balancing of an optics carrier carrying the surgical microscope, at least one pivot support encompassed by the displacement unit, and a displacer for displacing the optics carrier in an X direction extending horizontally and transversely to the oblique pivot axis. The pivot support comprises a pivotable parallelogram support and a holding arm that is attached to the pivotable parallelogram support and is configured such that it simultaneously serves as a displacer for displacing the optics carrier in the X direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of the German patent application DE102008011639.4 having a filing date of Feb. 28, 2008, the entire contentof which is herewith incorporated by reference.

BACKGROUND OF THE INVENTION

The invention relates to a stand, in particular for a surgicalmicroscope.

A “stand” for purposes of the invention is a floor or wall stand or aceiling mount.

Surgeons are increasingly making use of surgical microscopes that,because of their heavy weight, must be supported by stands. A number ofreputable manufacturers, in addition to the Applicant, have brought tomarket stands that competently meet the load-bearing requirements of asurgical microscope in mechanical and static terms.

As is known, for example, from DE 101 33 018 A1, many conventionalstands—e.g. those for surgical microscopes for ophthalmology—carry attheir free end, between the microscope and the vertical stand support,an X and/or Y shifting unit for the microscope. This shifting unitserves for positioning the microscope, within millimeters, in the Xand/or Y direction (in the plane parallel to the floor). An arrangementof this kind of the X-Y shifting unit (only the X shifting unit in thecase of DE 101 33 018 A1 (FIG. 2)) is usually obtrusive for an operator,since the shifting unit means that a relatively large mass and a largevolume must be moved, specifically not only the surgical microscope butalso the entire suspension system, pivot support, etc. It is furthermoredifficult, with this, to meet the necessary sterility requirements. TheX displacement area must in some circumstances be operated by thesurgeon, i.e. he or she must access it. This area remote from thesurgical field must therefore also be kept completely sterile, whichrequires a drape. The latter is, however, in turn an impediment tovision and to the operation of controls. The X(-Y) displacement unitfurthermore, because of its solid construction, considerably increasesthe weight on the horizontal extension arm, and as a rule must becompensated for by a corresponding compensation weight or braced by acorrespondingly large stand foot. The entire carrier arm structure ofthe stand support, and if applicable also the entire stand basestructure, must consequently have greater dimensions or must bedimensioned with a greater area. This all works against easyoperability.

ENT surgical microscope (microscopes for ear, nose and throat surgery)must be easy to move because a relatively large number of adjustmentsmust be made. In addition, such surgical microscope need to be fairlyeconomical, since fewer resources are available for ENT surgicaloperations than in, for example, the neurological sector.

DE 92 19 240 U1 describes a displaceable stand for an opticalobservation device, having a flange for mounting the displaceable standonto a stand base, onto a further stand, or onto the ceiling or a wall.The stand possesses a tilt joint about a horizontal tilt axis and apivot joint about a pivot axis, by way of which the observation deviceis received rotatably and/or pivotably on the flange. The pivot joint isconnected to the tilt joint with a rigid support extending obliquelydownward. The observation device consequently cannot be displaced in adirection perpendicular to the drawing plane, which greatly limits thepositional changes necessary during operation, and therefore themanageability of the observation device.

A “pivot support” is understood as that component or component groupwhich is installed indirectly or directly on the horizontally extendingsupport arm of the stand and receives, via an (in principle, horizontal)horizontal axis (A axis), the optics carrier in which the surgicalmicroscope is held. The optics carrier and thus the surgical microscopeare thus pivotable about this horizontal axis (A axis) and are thusintended to be tiltable with reference to that horizontal axis andbalanceable preferably in two planes, so that with the brakes released,a surgeon can pivot the optics carrier and thus the surgical microscopeabout the horizontal axis in as resistance- and torque-free a manner aspossible.

The horizontal axis is usually embodied at the lower part of the pivotsupport and equipped with a braking device or locking device thatprevents any unintentional pivoting movement of the optics carrier andthus of the surgical microscope with reference to the pivot support.

The problem set forth in conjunction with DE 92 19 240 U1 is remedied inpart by the technical approach described in DE 101 33 018 A1, whichpresents a stand, in particular for surgical microscopes, that isequipped with a stand base, a vertical support, one or more horizontalsupports, a pivot support, and an X-Y-Z displacement unit (FIG. 3) forbalancing on the pivot support. Displaceable X, Y, and Z displacementunits are provided therein which position the optics carrier, and themicroscope body installed thereon, in three dimensions.

In another variant of DE 101 33 018 A1 (FIG. 2), the horizontaldisplacement unit on which the pivot support can be displaced in ahorizontal X direction is arranged not at the free end of the pivotsupport but on the upper part of the pivot support. This displaceabilityserves for balancing about an (if applicable) oblique vertical axis (cf.the rigid oblique support of DE 92 19 240 U1) about which the pivotsupport, and thus the horizontal axis and thus the optics carrier andthe microscope, are pivotable. This pivoting movement, too, can beblocked by means of a brake or a locking device. The surgical microscopeis thus pivotable in two spatial directions about the axes with thebrakes or locking devices released, and can be balanced across therespective pivot axes.

A non-negligible disadvantage of the approach set forth results,however, from the physical dimension of the horizontal displacement unitfor X shifting. Shifting of the pivot support in one direction is easilyenabled, but this construction blocks or impedes a clear view by thesurgical personnel of, for example, important observation areas, orimpedes eye contact between surgeons and assistants. The relativelyhefty unit also increases the moving mass of the stand, which must beaccounted for in the strength calculations for all relevant components.

In the context of so-called “draping,” i.e. covering the entire standwith a sterile cloth, it is also disadvantageous when larger mechanicalexternal accessories are present in the region of the adjusting devices,since the drape can then become even more visually obtrusive.

To ensure better vision for the operator, DE 103 00 620 A1 proposesinterconnecting the articulation units at the end of the horizontalsupport arm with the microscope holder unit via a laterally curvedsupport. Because of its C-shaped appearance, such a support is alsocalled a “C support.” With this approach, an X-Y displacement unit isindeed moved closer to the vertical stand support so that the X-Ypositioning unit moves not only the microscope but additionally alsopart of the horizontal stand support, but this construction also doesnot yield easy and precise adjustment of the microscope along theaforesaid X direction. Inertia has a very obtrusive effect in thiscontext. This construction therefore also does not possess a completebalancing apparatus for the surgical microscope.

EP 0628290 presents a very complex stand apparatus for an item ofmedical/optical equipment. It encompasses a pair of vertical parallellinks and a pair of horizontal parallel links, which are combined withone another to form a parallelogram support. An intermediate portion ofone of the vertical links is connected pivotably, at a pivot point, to astand that is arranged on a surface. A counterweight is provided inorder to equalize the weight. The parallelogram support is thus equippedso as to hold the medical/optical equipment item in stationary fashionin a floating state. One of the horizontal links of the parallelogramsupport is elongated in order to form a support link, and asubstantially vertical front link is mounted pivotably on the supportlink at a front end thereof, the medical/optical equipment item beingheld at the lower end of the front link. The approach that is proposedcontributes to easy and precise displacement of the microscope in avertical direction, but a similar displacement capability in thehorizontal direction, i.e. along the X direction, is still not provided.

EP 0917451 B1 describes a pivot support for a surgical microscope on astand having vertical and horizontal supports with a suspension system.A prerequisite for the approach indicated therein was principally todispense with parallelogram supports and avoid their disadvantages, andnevertheless to enable torsion-free mounting of a surgical microscope.For that purpose, the parallelogram support was replaced by acombination of two two-armed angled levers, which are rotatablyinterconnected and which additionally receive at both ends identicallever gearing systems which transfer the moments so that (in a mannercomparable to a parallelogram support) the center of gravity of the loadcan be held in space. The two-armed angled lever is, however,constructed with great complexity from many precise components, and hasdimensions approximately comparable to those of the aforementioned X(horizontal) displacement unit of DE 101 33 018 A1.

SUMMARY OF THE INVENTION

A first goal of the invention is therefore to create a stand, inparticular for surgical microscopes, that one the one hand enablesunimpeded movement of the microscope in space, and on the other handdoes not impede a clear view by operating personnel of the area to beobserved.

Proceeding from the aforementioned existing art, it is thus a firstobject of the invention to modify the support structure of the stand insuch a way that the support units used ensure an appropriate andbalanceable displacement of the optics carrier along an X direction, butat the same time, because of their relatively small, slender dimensions,do not represent barriers to a view of, for example, co-workers orpatients.

The inventor has recognized that the horizontal displacement unit,arranged in the upper region, of DE 101 33 018 A1 can be replaced by alateral pivoting movement of the pivot support. The use of aparallelogram support instead of the previously only one-part pivotsupport ensures, according to the present invention, that the respectivehorizontal position of axis A (cf. FIG. 2 of DE 101 33 018 A1), and thusthe vertical position of the microscope holder or optics holder and ofthe microscope, remains unchanged and does not tilt away to the side.

This first object is thus achieved by a pivot support that comprises adisplaceable (pivotable) parallelogram support and a holding arm,mounted thereon, that is equipped so that it simultaneously serves as ameans for displacing the optics carrier along the X direction.

The MC1 of the existing art also exhibited a further problem, however:

In order, however, to enable sufficient balancing for the surgeon even,and especially, in those configurations of the system in which, forexample, assistant's tubes or lateral add-on units are to be attached tothe optics carrier, a consequence of the known arrangement according tothe MC1 is that these add-on units can collide, during the balancingprocedure, with the slide that is responsible for vertical displacement.The freedom of movement of the microscope was therefore limited in thecase of the known unit. On the other hand, homogeneity of the movementswas thereby also reduced.

In accordance with the existing art in the context of the MC1, in orderto reduce this problem the procedure of balancing out was made easier byattaching an add-on weight. The add-on weight, with its mass ofapproximately 3.5 kg, was attached on the side of the optics carrierlocated opposite the add-on units on the microscope. The add-on unitswere thus balanced out across the A axis at least in terms of the Ydirection (with the microscope in the normal position).

The disadvantage of this known weight compensation is that itconsiderably increases the total weight, which results in increasedinertia when pivoting. Installation or removal of this add-on weightalso required additional effort. This method is thereforetime-consuming, and moreover results in increased forces and moments onthe stand as a whole because of the greater total weight (see also e.g.EP-0476551 A1). The add-on weight produces not only an increase intorque (moment of resistance to rotation) during the displacementprocedure, but also greater friction in every bearing of the entirestand, thus increasing the overall inertia of the stand and limiting itsmobility. Homogeneity of the movements of the stand is also therebyreduced. In addition, the dimensions of the carrier arms of the stand(and of all other load-bearing components) of course also had to becorrespondingly enlarged, which in turn considerably increased the totalweight of these components and thus also the cost of the stand.

In present-day surgical practice, however, surgical microscopes not onlyneed to meet standard requirements in terms of optical quality, brightillumination, compact design, and maximum flexibility, but also mustincorporate additional operational aspects. Consideration must now begiven, for example, to the fact that the number of surgical operationsper day has risen. The time needed to set up a surgical microscope forthe next operation is becoming increasingly important. As an essentialcomponent of the operating-room infrastructure, the surgical microscopehas a significant influence on costly preparation time.

The second object underlying the invention is therefore that of evenfurther improving an apparatus that has been improved in accordance withthe first object, which apparatus enables relatively faster and simpler,and complete, balancing of the surgical microscope without an add-onweight. This is intended to significantly reduce or eliminate theaforementioned disadvantages of the existing art. The intention istherefore for all possible configurations of the surgical microscope tobe as easy as possible for the surgeon to balance out across the A axis.

The inventor has further recognized that in order to achieve the secondstated object, weight must be reduced at least in the region of theoptics carrier, without limiting movements for a precise balancingprocedure. In particular, the intention was to remove the additionalcompensation weight. If this were successful, then in combination withthe aforesaid manner of achieving the first object, an ideal design forthe surgical microscope would be found. This second object is notachieved or suggested by any of the known balancing device, especiallybecause this object had not hitherto been stated in any of the knowndocuments (including DE 10133018 A1) of the existing art. In addition toreplacement of the add-on weight, a further intention is therefore toprioritize weight saving, cost reduction, and smooth operation of thestand.

This second object is achieved, according to the present invention, byan aforementioned stand, further comprising a balancing apparatus for asurgical microscope for balancing an optics carrier held by the pivotsupport, said optics carrier being rotatable around a first rotationalaxis in relation to the pivot support; said balancing compensating forthe use with and without a microscope holder holding the surgicalmicroscope and with and without add-on units, the balancing apparatuscomprising: a Y displacement unit comprising a first slide fordisplacement of the optics carrier in a Y direction; and a Zdisplacement unit comprising a second slide for displacement of theoptics carrier in a Z direction, wherein the first slide provides fordisplacement of the optics carrier in a direction transversely to thefirst rotational axis and transversely to the displacement by the secondslide in the Z direction; and the first slide is connected between thepivot support and the second slide and to said second slide such thatthe weight of the second slide acts as a compensation weight forcompensating the weight of the optics carrier with and without themicroscope holder holding the surgical microscope and with and withoutthe add-on units via the first rotational axis.

The invention in accordance with the first and the second object isfurther explained, symbolically and by way of example, with reference tothe attached FIG. 6. It is to be understood that the measures forachieving the first object can be integrated into the embodimentsaccording FIGS. 1 to 5 below, but are not absolutely necessary, sincethe novel X displacement system itself already provides a significantand inventive improvement with respect to existing balancingapparatuses.

Be it also noted expressly at this juncture that the overallconstruction of the stand can be even further improved by the fact thatin addition to the two inventions indicated above, a third invention isalso integrated. This is described in U.S. patent application Ser. No.12/371,518 filed on Feb. 13, 2009. Reference is made with this presentpatent application to the aforementioned patent application. Referenceis also made to a further U.S. patent application Ser. No. 12/371,440filed on Feb. 13, 2009. All the inventions in accordance with thesethree patent applications can advantageously be integrated for optimumconfiguration of a stand, for which reason the contents of the twoaforementioned

The Parts List, together with the content of the Claims, is aconstituent of the disclosure.

The invention will be further explained, symbolically and by way ofexample, with reference to Figures. The Figures are describedcontinuously and in overlapping fashion. Identical reference charactersdenote identical components; reference characters having differentindices indicate similar or functionally identical components.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows the overall configuration of a surgical microscope having astand base, vertical support, control unit, horizontal support, pivotsupport, and microscope unit;

FIG. 1 a shows a configuration in accordance with the manner ofachieving the second object (slide arrangement S1, S2);

FIG. 2 is a perspective plan view of an embodiment of the pivot supportaccording to the present invention of FIG. 1;

FIG. 3 is a side view of the pivot support of FIG. 2 from the samedirection as in FIG. 1;

FIG. 4 is a further depiction of the pivot support of FIG. 2;

FIG. 5 shows the parallelogram support of the pivot support of FIG. 4 atenlarged scale; and

FIG. 6 shows the configuration according to the present invention inaccordance with the manner of achieving the first object, with theaddition of a novel slide arrangement according to the second object.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic general configuration of a surgicalmicroscope according to the present invention. A stand base 1 is visibleherein, from which a vertical support 2 protrudes. For convenientmovement of the caster-mounted stand, a grip 3 is attached to verticalsupport 2. Installed on vertical support 2 is a control unit 4 on whichhorizontal supports 5 are braced. In the embodiment depicted, thehorizontal supports end in an articulation unit 6 that holds a pivotsupport 7, with optics carrier 9 mounted thereon, pivotably about apivot axis S. Located at the other end of pivot support 7 is Y-Zdisplacement unit 8. The binocular tube having eyepieces 10, and anergonomically shaped handle 11, are also depicted.

FIG. 1 a shows, in the upper part, a configuration according to themanner of achieving the second object (slide arrangement S1, S2) that ispreferably arranged at the lower end of pivot arm 7. Regarding furtherdetails of this configuration, the reader is referred to the Figures ofU.S. patent application Ser. No. 12/371,440 filed on Feb. 13, 2009.

FIG. 2 depicts pivot support 7 in a perspective plan view. Pivot support7 comprises at its upper end, adjacent to horizontal support 5, an axispin 12 with which pivot support 7 is rotatably mounted and held invertical articulation unit 6. Axis pin 12 adjoins a further articulationunit 13 that mounts pivot support 7 rotatably about the S axis (theactual pivot axis) drawn with a dot-dash line in FIG. 1. Attached toarticulation unit 13 is a further displacement unit 14 that serves forpositioning of a parallelogram support 15. Parallelogram support 15 ismovably connected at its other end to a holding arm 16, and the lattercarries at its other, lower end a further articulation unit 17 thatrotatably mounts Y-Z displacement unit 8 (see FIG. 1). Displacement unit14 comprises a displacement screw 18 that is connected, in a manner tobe presented in more detail below, to a displacement element 19. In theexemplifying embodiment depicted, displacement element 19 is fixedlyconnected to parallelogram support 15. In the example depicted, holdingarm 16 is connected via pivot pins 20 a, b to movable parts 21 ofparallelogram support 15 in the interior of the body of parallelogramsupport 15.

FIG. 3 is a side view of pivot support 7 from the same direction as inFIG. 1, i.e. from the left. As is evident, pivot support 7 extendsobliquely downward, approximately parallel to the orientation of pivotaxis S. Further articulation unit 17 contains a sleeve for reception ofa corresponding pin of Y-Z displacement unit 8 (not depicted).

FIGS. 4 and 5 show a further depiction of pivot support 7 in which theinternal components of parallelogram support 15 are drawn with dashedlines. Movable parts 21 of parallelogram support 15 are arranged insidethe body (bent from sheet metal in the embodiment depicted) and, as isusual for parallelogram links or parallelogram supports, interconnectedvia pivot pins 20. In order to achieve easier operation for X-directiondisplacement by means of displacement screw 18, at least one energyreservoir 23, which is attached via mounting eyes 22 to the body and tomovable part 21, is also located in the interior of the body. Incontrast to conventional parallelogram supports having an energyreservoir, this energy reservoir does not have a bracing function in theenergy-storage direction against the weight of the surgical microscope,but instead has exclusively the function of facilitating displacement ofthe displacement screw. The displacement screw accordingly is preferablyself-locking.

Instead (or alternatively), or for assistance of the energy reservoir,an electric motor could also be provided in the context of a furtherdevelopment of the invention. In the alternative case, the electricmotor can also take on the function of the displacement screw, in whichcase the electric motor (energy reservoir) also takes on a bracingfunction. It is preferred in this case if the electric motor is embodiedin self-locking fashion, so that no unintentional displacement can occurin the zero-current state.

A variety of components known to one skilled in the art are usable asenergy reservoir 23. A helical spring or a gas spring, for example, canbe used. If a gas spring is used, less energy expenditure is necessaryupon displacement of displacement screw 18. In a preferred exemplifyingembodiment, displacement screw 18 is motor-driven. Energy reservoir 23could then actually be omitted if movable parts 21 are installed with atight fit relative to the body of parallelogram support 15, and if theposition of parallelogram support 15, once established, is maintained bythe friction that exists.

FIG. 6 shows the configuration according to the present inventionaccording to the manner of achieving the first object, with the additionof a novel slide arrangement according to the second object (cf. FIG. 1aand Patent Application 10 2008 011 640, submitted on the same date).Thanks to this configuration, the surgical microscope becomes optimallybalanceable in six degree of freedom.

When the surgical microscope is in service, movements of the surgicalmicroscope can be performed in the three principal directions X, Y, andZ. The three principal directions X, Y, and Z are to be understood asfollows: the X direction as approximately left-right in the plane of thedrawing with respect to the observer, the Y direction as a directionfront to back and perpendicular to the drawing plane, and the Zdirection as an up and down direction approximately parallel to the Xdirection.

In the example depicted, the position of parallelogram support 15 andthus of pivot support 7 is determined, or modified or aligned, by way ofdisplacement screw 18. Clockwise rotation of displacement screw 18causes displacement element 19 to move away from displacement unit 14,with the result that parallelogram support 15, loaded by energyreservoir 23, pivots to the right in FIG. 2, i.e. along direction X,since although the orientation of holding arm 16 remains unchanged, itslongitudinal axis is shifted parallel to itself. Counterclockwiserotation of displacement screw 18 causes displacement element 19 to bepulled closer to displacement unit 14 by means of displacement screw 18.Parallelogram support 15, fixedly connected to displacement element 19,is thereby pivoted to the left in FIG. 2, i.e. once again alongdirection X, against the force of energy reservoir 23, and theorientation of holding arm 16 remains unchanged. By means of anappropriate embodiment of displacement screw 18, a coarse but also afine adjustment or alignment of pivot support is accomplished. In thecontext of the invention these displacement screws can of course also bereplaced by electric drive systems, and operated remotely.

With the new pivot support 7, instead of the previous linear transversemotion in the upper region of pivot support 7, a pivoting motion iscarried out in the lower part of pivot support 7 and causes opticscarrier 9 to pivot along an arc about an axis in the upper region ofpivot support 7. But because the upper part of pivot support 7 isembodied, according to the present invention, as a parallelogramsupport, the pivot axis remains in the lower part of pivot support 7 inan unchanged, preferably horizontal, position.

The principal advantage of the proposed solution that can be mentionedis that the previously utilized complete horizontal displacement unit inthe vicinity of the upper articulation units, in addition to the pivotsupport, is eliminated; and the displacement parts that enable thispivoting movement have only a minimal physical size and therefore do notrepresent an obstacle to vision or the like. According to a particularembodiment of the invention, the parallelogram support is constructed innested fashion, so that only a portion of the link is visible. Thiscontributes to a more robust construction and to a lower risk ofcontamination. The parallelogram support furthermore ensurescorresponding rigidity in directions deviating from its plane, whichmakes the dimensioning of pivot support 7 easier and ultimately meansthat lower forces are acting on the stand. A parallelogram supportsystem of this kind can moreover be completely (perfectly) balanced byfirstly moving the center of gravity of the microscope onto axis A (Y-Zdisplacement), then bringing axis A into intersection with axis S andthen shifting it transversely to axis S until the center of gravity ofthe microscope is also located on axis S. In this location themicroscope is perfectly balanced in three axes and is thereforepractically weightless for the operator.

The Parts List below is a constituent of the description. Theconstructions, apparatuses, and details indicated in the Claims are alsodeemed to be disclosed as if in the context of the description.

The reference characters in the aforementioned mutually referencedApplications of the same application date may differ slightly betweenthe Applications. This does not mean, however, that the componentsbearing the different reference characters in the different applicationsare differently configured.

List of Component Parts

-   1 Stand base-   2 Vertical support-   3 Grip-   4 Control unit-   5 Horizontal support-   6 Articulation unit-   7 Pivot support-   8 Y-Z displacement unit-   9 Optics carrier-   10 Eyepiece-   11 Handle-   12 Axis pin-   13 Articulation unit-   14 Displacement unit-   15 Parallelogram support-   16 Holding arm-   17 Articulation unit-   18 Displacement screw-   19 Displacement element-   20 a, b Pivot pins of parallelogram support-   21 Movable part-   22 Mounting eye-   23 Energy reservoir-   S Pivot axis

The invention claimed is:
 1. A stand for a surgical microscope,comprising: a vertical support; the vertical support further comprisesat least one horizontal support having a first end facing toward thesurgical microscope; a first vertical articulation unit that isconnected said first end; a second articulation unit determining anoblique pivot axis and being connected to the first verticalarticulation unit; a displacement unit that is attached to the secondarticulation unit and has multiple degrees of freedom for displacementand balancing of an optics carrier carrying the surgical microscope; atleast one pivot support encompassed by the displacement unit; and meansfor displacing the optics carrier in an X direction extendinghorizontally and transversely to the oblique pivot axis, said means fordisplacing being provided at the pivot support; wherein said pivotsupport comprises: a pivotable parallelogram support having a firstcarrier arm and a second carrier arm, the second carrier arm extendingin parallel to the first carrier arm; and a holding arm that is attachedto the pivotable parallelogram support and is configured such that itsimultaneously serves as a means for displacing the optics carrier inthe X direction; wherein the pivot support is attached with a first enddirectly to the second articulation unit and with a second end directlyto a Y-Z displacement unit for the optics carrier.
 2. The standaccording to claim 1, wherein the pivot support is provided with anadditional displacement unit that determines the position of theparallelogram support with reference to the second articulation unit. 3.The stand according to claim 2, wherein the additional displacement unitcontains a displacement screw that protrudes through the parallelogramsupport and is connected in an articulated fashion at one of its ends toa displacement element mounted to the parallelogram support.
 4. Thestand according to claim 2, wherein the additional displacement unitcomprises an electric drive system.
 5. The stand according to claim 3,wherein at least one of the movable parts of the parallelogram supportand of the displacement screw are self-locking maintaining positions ofthe parallelogram support by a self-locking force.
 6. The standaccording to claim 1, wherein the parallelogram support is provided withan energy storing device assisting with a stored force in a displacementmovement.
 7. The stand according to claim 6, wherein the energy storingdevice is at least one of a spring and a gas damper that interconnectsand supports movement of the movable parts in the interior of theparallelogram support.
 8. The stand according to claim 6, wherein theenergy storing device comprises an electric motor.
 9. The standaccording to claim 1, wherein the parallelogram support has a closed,integrated design having the first carrier arm arranged inside thesecond carrier arm.
 10. The stand according to claim 1, wherein thedisplacement unit has six degrees of freedom.
 11. The stand according toclaim 1, further comprising a balancing apparatus for a surgicalmicroscope for balancing an optics carrier held by the pivot support,said optics carrier being rotatable around a first rotational axis inrelation to the pivot support; said balancing compensating for the usewith and without a microscope holder holding the surgical microscope andwith and without add-on units, the balancing apparatus comprising: a Ydisplacement unit comprising a first slide for displacement of theoptics carrier in a Y direction; and a Z displacement unit comprising asecond slide for displacement of the optics carrier in a Z direction,wherein the first slide provides for displacement of the optics carrierin a direction transversely to the first rotational axis andtransversely to the displacement by the second slide in the Z direction;and the first slide is connected between the pivot support and thesecond slide and to said second slide such that the weight of the secondslide acts as a compensation weight for compensating the weight of theoptics carrier with and without the microscope holder holding thesurgical microscope and with and without the add-on units via the firstrotational axis.
 12. The stand according to claim 11, wherein the opticscarrier is connected to the slide of the Z displacement unit and movablevia said slide.
 13. The stand according to claim 11, wherein the firstslide has a first guidance element and a first insert axiallydisplaceable in the first guidance element, the first insert is securedto a second guidance element of the second slide, a second insert of thesecond slide is arranged axially displaceably in said second guidanceelement, and the second insert is connected to the optics carrier. 14.The stand according to claim 11, wherein the optics carrier along withthe second slide is held by a holding part that carries in integratedfashion an electronic system and at least one sensor for motors forremote operation of the first and second slides.
 15. The stand accordingto claim 13, wherein the second insert and the optics carrier areintegrally formed.
 16. The stand according to claim 11, wherein thefirst and the second slide are combined into a cross-slide and the firstinsert of the first slide is integrally formed with the second guidanceelement of the second slide.
 17. The stand according to claim 11,wherein the drive systems for the first and second slides areelectrified and drivable in sensor-controlled fashion by remote control.